General-purpose registers are represented by predefined symbols of the
form r
N (for global registers), where N represents
a number between
0
and 15
. The leading
letters may be in either upper or lower case; for example, r13
and R7
are both valid register names.
Register names PC
, SP
and SR
cannot be used as register names
and will be treated as variables. Use r0
, r1
, and r2
instead.